arsis
/ˈɑːsɪs
/noun (plural arses /ˈɑːsiːz/) Prosody
A stressed syllable or part of a metrical foot in Greek or Latin verse. Often contrasted with thesis (sense 3).Comparable to the inversion of geometric patterns, a melodic line could be played in reverse order (temporal thesis) or inverted and presented as the mirror image of the original (temporal arsis).
Origin
Late Middle English: via late Latin from Greek, literally 'lifting', from airein 'raise'.